
where \(\mathbf {m}_{s \rightarrow t}\)  and \(\mathbf {\mu }_{s^{\prime } \rightarrow t^{\prime }}\)  are
intra-graph and inter-graph messages, respectively.
Intra-graph message passing can be defined in a similar way following standard GNN architectures, like GIN [1]}.
While
for \(\operatorname{MSG}_{\operatorname{inter}}\) , we adopt a cross-graph attention mechanism as:
\(\mathbf {\mu }_{s^{\prime } \rightarrow t^{\prime }} =&\ a_{s^{\prime } \rightarrow t^{\prime }}\cdot \mathbf {h}_{s^{\prime }}^{(1)},\) 
